• 대한전자공학회논문지
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• 제26권3호
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• pp.95-104
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• 1989

본 논문은 3차원적 분할공간 환경에서 종래의 음영검사법과 Crow의 음영입체법을 상황에 따라 우리하도록 선택하는 혼합음영검사법을 소개하고 파라메타화를 통하여 그 선택의 최적화를 꾀하였다. 추가적인 선행계산시간이 소요됨에도 불구하고 제안된 혼합음영검사법은 여러가지 예제화면들에 재하여 종래의 방법에 비하여 음영계산시간에 있어서는 50%, 전체묘화시간에 있어서는 30%정도씩의 CPU시간단축효과를 보였다. 그 원인은 음영검사의 선택적 사용을 통하여 그림자영역의 일관성(coherency)을 이용한데에 있다. 연속되는 두 반사점사이에 존재하는 음영다각형의 갯수를 나타내는 $N_{th}$라는 파라메타가 음영검사의 효과적 선택을 위한 지표가 되며, 묘화환경의 통계적 수치로부터 이 값을 알아내는 방법이 제안되고 실험적 결과와 비교된다.

• 천문학논총
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• 제30권2호
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• pp.389-392
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• 2015

We identify a strong lensing galaxy in the cluster IRC 0218 that is spectroscopically confirmed to be at z = 1.62, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be $z_S=2.26$. Using HST imaging, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is $^{\theta}E=0.38^{+0.02{\prime}{\prime}}_{-0.01}$ ($3.2^{+0.2}_{-0.1}kpc$) and the total enclosed mass is $M_{tot}(<^{\theta}_E)=1.8^{+0.2}_{-0.1}{\times}10^{11}M_{\odot}$. We estimate that the cluster environment contributes ~ 10% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within $^{\theta}E$ is $f^{Chab}_{DM}=0.3^{+0.1}_{-0.3}$, while a Salpeter IMF is marginally inconsistent with the enclosed mass ($f^{Salp}_{DM}=-0.3^{+0.2}_{-0.5}$).

• 천문학회보
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• 제37권2호
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• pp.80.2-80.2
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• 2012

홀로 고립되어 존재하는 은하는 주변 은하와 상호작용을 하지 않은 채 진화하므로 은하의 진화를 연구하기에 아주 좋은 대상이다. 은하의 정량적 연구를 위해 꼭 알아야 하는 중요한 물리량으로 거리와 성간소광량이 있다. 우리는 허블 우주망원경(HST) Advanced Camera for Surveys(ACS)/High Resolution Channel(HRC)로 관측한 고립된 왜소불규칙은하 NGC 1156 ($RA_{2000}$=02:59:42.19, $DEC_{2000}$=+25:14:14.2) 중심부($26^{\prime\prime}{\times}29^{\prime\prime}$)의 archive 자료를 분석하여 이 은하의 거리와 성간소광량을 새로 구했다. 이 은하의 거리를 측정한 과거 자료는 Tully(1988, Nearby Galaxies Catalog) 목록과 Special Astrophysical Observatory 6m 망원경/VI(각 300s) 영상자료의 가장 밝은 별로 거리를 구한 Karachentsev et al. (1996) 자료 뿐이다. 우리는 HST/ACS/HRC+UBVI 자료 중 U자료를 이용하여 아주 신뢰할 만한 소광량 값($E(B-V)=0.35{\pm}0.05$)을 얻었고, 가장 밝은 빨간 별과 파란 별 자료를 이용하여 새로운 거리지수($(m-M)_0=29.39{\pm}0.20$, $d=7.6{\pm}0.7$ Mpc)를 결정했다. 이 거리 값은 과거의 값들(Tully $6.4{\pm}1.2$ Mpc; Karachentsev et al. $7.8{\pm}0.5$ Mpc)과 크게 다르지 않으며, 기존의 거리 자료들 역시 신뢰할만함을 보여준다. ACS/Wide Field Channel과 달리 ACS/HRC의 경우 등급 표준화 방정식이 완벽하지 않은데, 우리의 경우 F550M자료를 표준화할 수 없었다. 그러나 우리는 여러 파장, 많은 관측자료가 존재하는 47 Tucanae (NGC 104) 구상성단의 관측자료와 Padova 등연령곡선을 이용하여 성공적인 등급변환을 수행할 수 있었다.

• 천문학회보
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• 제37권2호
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• pp.68.1-68.1
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• 2012

We present a comprehensive study of the stellar populations in two faint M31 dwarf satellites, And XI and And XIII. Using deep archival images from the Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telepscope (HST), we characterize the horizontal branch (HB) morphologies and the RR Lyrae (RRL) populations of these two faint dwarf satellites. Our new template light curve fitting routine (RRFIT) detected RRL populations from both galaxies. The mean periods of $RR_{ab}$ (RR0) stars in And XI and And XIII are < $P_{ab}$ > = $0.621{\pm}0.040$, and < $P_{ab}$ > = $0.648{\pm}0.038$ respectively. Even though the RRL populations show a lack of $RR_{ab}$ stars with high amplitudes (Amp(V) > 1.0 mag) and relatively short periods ($P_{ab}$ ~ 0.5 days), their period - V band amplitude (P-Amp(V)) relations track the lower part of the general P-Amp(V) trend in the M31 outer halo RRL populations. The metallicities of $RR_{ab}$ stars were calculated via the [Fe/H]-log $P_{ab}$-Amp(V) relationship of Alcock et al. The metallicities thus obtained ($[Fe/H]_{And}$ $_{XI}=-1.75%$; $[Fe/H]_{And}$ $_{XIII}=-1.74$) are consistent with the values calculated from the RGB slope indicating that our measurements are not significantly affected by the evolutionary effects of RRL stars. We discuss the origins of And XI and And XIII based on a comparative analysis of the luminosity-metallicity (L-M) relation of Local Group dwarf galaxies.

• 한국산학기술학회논문지
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• 제20권5호
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• pp.66-72
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• 2019

동력 집중식 고속 철도차량의 승차감과 주행 안정성 향상 방안으로서 채택한 관절형 대차는 차체와 결합된 기존 독립대차와 달리 객차 사이를 갱웨이 링에 의하여 연결한다. 갱웨이 링은 열차 주행 동안 객차분리를 방지하면서 객차사이 승객 이동에 대한 절대적 안전을 확보되어야 함에도 불구하고, 아직까지 정량적인 내구성 시험기준 설정이 미비하다. 따라서 동력 집중식 고속 철도차량의 승차감과 승객 안전성을 향상을 위해서는 관절형 대차 갱웨이 링에 대한 내구성 평가의 시험기준에 대한 체계적인 연구가 중요하다. 본 연구에서는 고속 철도차량 관절형 대차의 갱웨이 링에 대한 안전성을 검토하기 위하여, 열차 운행조건에 준한 전후, 좌우 및 수직의 3축 모드로부터 7가지 혼합모드 하중조건을 도출하였다. 이 하중조건하에 유한요소해석결과로부터 각 부품들의 안전율은 최소 2.4 이상이다. 또한 변형률-피로수명설계관점에서 내구성 해석을 통하여 피로안전성을 평가하였다. 본 갱웨이 링에 대한 내구성 시험은 혼합모드 하중조건하에 총 4단계의 1,000만 사이클을 수행하였다. 내구성 시험 후에 침투 탐상 검사기법을 이용하여 각 부품의 결함유무를 검토하였다.

• Wind and Structures
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• 제35권2호
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• pp.83-92
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• 2022

When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ=3.2 m based on a 1/20^th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37×10⁶ to Re = 1.45×106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ=0° to γ=4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ=0° to γ=4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.

• Journal of Plant Biology
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• 제14권4호
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• pp.14-18
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• 1971

Lilium Miquelianum Makino is a species which originated in Korea. The Karyotype of the species was examined in materials collected at Mts. Kaya, Kasan, Chejung, and Kaji. The results are as follows: 1) The somatic chromosome number was found to be 2n=24. 2) The karyotype is described as: K=2Am＋2Bkm＋2Csst＋2Dsst＋2Ests＋2Fst＋2Gst＋2Hst＋2Ist＋2Jsst＋2Kst＋2Lst m: metacentric, sm: submetacentric st: subtelocentric, s: secondary constriction 3) A single subcentric supernumerary B-chromosome was found in some bulbs from Mt. Kasan. 4) The shape of the supernumerary B-chromosome was similar to that of the E chromosome which had separated at its secondary constriction and lost its lower chromosome fragment. 5) From three to eight nucleio of varying sizes were found in the telophase or interphase nucleus of root tip cells. The maximum number of eight nucleoli corresponds to the number of chromosomes that have a secondary constriction.

• 천문학회보
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• 제38권2호
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• pp.42.2-42.2
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• 2013

We investigate the cosmic evolution of the black hole mass-bulge luminosity relation with a sample of 52 moderate-luminosity AGNs at $z{\simeq}0.36$ and $z{\simeq}0.57$, corresponding to look-back times of 4 and 6 Gyrs. By employing robust multi-component spectral and structural decomposition methods to the obtained high-quality Keck spectra and high-resolution HST images, black hole masses ($M_{BH}$) are estimated from the Hbeta broad emission line with the 5100A nuclear luminosity, and bulge luminosities ($L_{bul}$) are derived from the surface photometry. Based on these consistent measurements, we constrain the redshift evolution of the $M_{BH}-L_{bul}$ relation by performing the Monte Carlo simulations designed to account for selection effects. We provide implications of our results in terms of the black hole-galaxy co-evolution and discuss possible bulge growth mechanisms.

• 천문학회보
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• 제38권2호
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• pp.70.1-70.1
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• 2013

We present long-term optical to NIR data of the tidal disruption object, Swift J1644+57. The data were obtained with CQUEAN, UKIRT WFCAM observations. We analyze the morphology of the host galaxy of this object and decompose the bulge component using high resolution HST WFC3 images. We conclude that the host galaxy is bulge dominant. We also estimate the multi-band fluxes of the host galaxy through the light curves based on the long-term observational data. We fit the SED models to the multi-band fluxes of the host galaxy and determine its stellar mass. Finally, we estimate the mass of the central super massive black hole which is thought to be the main role of the tidal disruption event. The estimated stellar mass and black hole mass are $10^{9.1}M_{\odot}$, $10^{6.8}M_{\odot}$ respectively. We compare our results to other results that have studied before.

• Journal of Mechanical Science and Technology
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• 제18권9호
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• pp.1614-1622
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• 2004

When a High Speed Train (HST) passes through a station with no stop, effects of wind pressure transients caused by this passing train have to be considered for the safety of passengers on the platform and for the possible structural safety problems as well. In Gwangmyeong and Daejeon stations of the Korean high speed railroad, tunnels inside stations for the passing train are proposed to reduce the noise and wind pressure transients to the passengers on the platform. In the present study, transient 3-D full Navier-Stokes solutions with moving mesh to implement train movement are obtained and compared with the results obtained by the towing tank experiment. Investigations on flow phenomena for various train speeds and design modifications are also performed.